When is radar service terminated for an IFR approach at an uncontrolled airport?

Answer: A — Only upon landing or advised to change to advisory frequency.

Radar service for an IFR (Instrument Flight Rules) approach at an uncontrolled airport is typically terminated only upon landing or when the pilot is advised to change to an advisory frequency. This is because the radar service is part of the Air Traffic Control (ATC) management of the flight's safety and navigational assistance during its approach. When transitioning to an uncontrolled airport, it is crucial for pilots to maintain their awareness and receive all necessary instructions until they have safely landed or until instructed to switch to an advisory frequency, which informs them they are now responsible for conducting their own traffic separation and navigation using the information available from the advisory service or their own judgment. The other options do not accurately describe the point at which radar service is terminated. Being aligned on the final approach course or being cleared for the approach does not change the fact that ATC maintains responsibility for providing radar services and separation until either of the specified conditions in the correct answer is met. Furthermore, exiting controlled airspace does not directly correlate with the termination of radar service for a landing at an uncontrolled airport, as service continues until landing or until the advisory frequency is engaged.